Pressing processes of said type are for example used in the pressing of tube ends or shaft connections. High pressing powers are required because the friction of a close fit must be overcome and, in many cases, an additional deformation of material must be brought about. A typical example is the pressing-in and pressing-out of collet chucks or sleeves into and out of corresponding tool or collet chuck holders in machine tools.
For certain embodiments of tool receptacles, in particular those with little or no conicity of the collet chuck and holding cone, such as are preferred for machines with very high rotational speeds, the collet chucks or sleeves with the inserted tool shank cannot be directly inserted into the receptacle of the collet chuck holder and fixed with a clamping nut, or inversely be extracted after the release of the clamping nut, but must be pressed in and out again with a high pressure.
There are various solutions for said pressing-in and pressing-out processes; on the one hand, those in which the devices for generating the required axial forces are part of the clamping device, and on the other hand, separate pressing-in and pressing-out devices. The latter have been fundamentally proven because they do not lead to a complication of the clamping device. A device of said type is for example known in which an insert, which engages coaxially around the parts which are to be pressed, in a pressing device holds suitable flanges of the parts which are to be moved towards one another. The insert itself can be inserted and removed through a closure door which is arranged on one side of the device, and is held closed during the pressing process by a pressure pin. The closure door is articulatedly mounted on the fixed pressure plate. The relative movement of the pressure pin with respect to the moving pad of the insert during the pressing process results, despite a friction-reducing spherical design of the pressure pin, in indentations in the material and in material wear. Furthermore, the pressure action on the moving pad changes during the pressing process, which can lead to its opening.